Lazy eye occurs when the brain does not fully acknowledge the images it sees from one of your eyes. This is because the brain does not receive images from the lazy eye in the way that it does from the healthy eye. This results in vision impairment and loss of depth perception.
The affected eye doesn’t necessarily look different, though it may “wander” in different directions. That’s where the term “lazy” comes from. The condition will usually only affect one eye, but in certain circumstances, the vision in both eyes can be affected.
The condition usually occurs in children. According to the Optometrists Network, three percent of children under age six will have some form of lazy eye (Cooper, 2012). It is important to note that lazy eye is not a crossed or turned eye. That condition is called strabismus. However, strabismus can lead to lazy eye if the crossed eye gets much less use than the uncrossed one.
Lazy eye is responsible for more loss of vision in people under 40 than all other injuries and diseases combined (Optometrists Network). If a lazy eye goes untreated, temporary or permanent loss of vision—including loss of depth perception and 3D vision—can occur.
The medical term for lazy eye is “amblyopia.”
Lazy eye is related to developmental problems in the brain. In this case, the nerve pathways in the brain that process sight do not function properly. This dysfunction occurs when both eyes do not receive the same amount of use. You may come to rely disproportionally on one eye as the result of one of the following factors:
- constant strabismus (constant turning of one eye)
- genetics (other family members have lazy eye)
- different levels of vision in each eye
- damage to an eye from trauma
- drooping of one eyelid
- a vitamin A deficiency
- a corneal ulcer or scar
- eye surgery
- vision impairment (being nearsighted, farsighted, or having astigmatism)
- glaucoma (high pressure in the eye that can lead to vision problems and blindness)
The eye that you use less becomes weaker or “lazy.”
Lazy eye may be hard to detect until it becomes severe. Early warning signs include:
- a tendency to bump into objects on one side
- an eye that wanders inward or outward
- eyes that appear not to work together
- poor depth perception
- double vision
Lazy eye usually occurs in only one eye. When it first occurs, parents and children often do not notice the condition. Failure to get your child’s eyes examined while he or she is an infant and toddler can contribute to further development of the problem. The American Optometric Association recommends that children have eye exams when they are 6 months and 3 years old (AOA).
Your doctor will typically perform a standard eye exam to assess vision in both eyes. This involves a series of tests such as:
- identifying letters or shapes on a chart
- following a light with each eye, and then both eyes
- having the doctor look at the eyes with a magnifying device
Your doctor is checking vision clarity, eye muscle strength, and how well the eyes focus, among other things. He or she will be on the lookout for a wandering eye or a difference in vision between the eyes. For most lazy eye diagnoses, an eye examination is all that is required.
Treating underlying eye conditions is the most effective way to treat lazy eye. This will require getting the damaged eye to develop normally. Early treatment measures are simple and may include eyeglasses, eye drops, vision therapy, and eye patches.
The earlier a child gets treatment, the better the outcome. However, recovery is still possible in cases that are diagnosed when children are older.
Treatment methods include:
If being nearsighted, farsighted, or having astigmatism in one eye is the reason behind the lazy eye, glasses or contact lenses may be prescribed.
An eye patch over the dominant eye can help strengthen the weaker eye. Most doctors will suggest that the patch be worn one to two hours a day, depending on how severe the lazy eye is. The patch will help develop the brain area that controls vision.
Drops may be used once or twice a day to cloud the vision in the healthy eye, which encourages use of the weaker eye. This is an alternative to wearing a patch.
Crossed eyes or eyes that point in opposite directions may require surgery on the muscles of the eye.